1. Field of the Invention
The present invention relates to a linear pulse motor, and more particularly to a core unit in a linear pulse motor and a method of manufacturing a core unit constituting a slider (primary side magnetic flux generator unit).
2. Description of the Prior Art
As is well known, a linear pulse motor forces a slider or a secondary side scale to linearly move stepwise in response to a pulse signal supplied to a slider coil.
FIGS. 3 and 4 are respectively a front view illustrating exemplary arrangement of a linear motor, and a side view illustrating the same. In the same figures, designated at 1 is a scale formed by a continuous plate, and 2 is a slider placed on the scale 1. The slider 2 consists of a core unit 3, coils 4, 4 . . . , each wound around the magnetic poles of the core unit 3, supporting shafts 5, 6 mounted on both end parts of the core unit 3, rotating rollers 7, 7 . . . , each mounted on both ends of these supporting shafts 5, 6, permanent magnets 8a, 8b mounted on the core unit 3, and a back plate 10 mounted on these permanent magnets 8a, 8b. In addition, the core unit 3 consists, as shown in FIG. 5, of first and second cores 12, 13, and of a nonmagnetic member 14 interposed between these cores 12, 13 for magnetically shielding both the cores. Thereupon, magnetic poles 12a, 12a . . . , are formed on the central portion of the core 12, and leg parts 12c each having concave grooves 12b are formed on both ends of the core 12. The supporting shafts 5, 6 are inserted into the concave groove 12b and fixed. Moreover, the nonmagnetic member 14 comprises resin for example.
Hereupon, the core unit 3 however suffered from the following drawbacks until now, since a binder injected between the cores 12 and 13 as the nonmagnetic member 14 and solidified.
(1) The use of a binder makes the core unit costly.
(2) Vertical positions of the cores 12, 13 do not completely agree with each other whereby a slight stepped portion is produced therebetween. This stepped portion is likely to produce any looseness when the supporting shafts 5, 6 are inserted into the concave groove 12b and fixed, and thus it is needed to remove the stepped portion between the bottom surfaces 12d, 13d of the respective concave grooves 12b, 13b formed in the cores 12, 13 by adequately processing these bottom surfaces 12d, 13d.
(3) The above stepped portion also produces another stepped portion between the magnetic pole surface of the core 12 (surface opposing to the scale 1) and that of the core 13. Accordingly, processing to remove this stepped portion is also necessary.
(4) The core unit 3 is likely to be warped upon the solidification of the binder.